The present invention is directed to flotation systems for purifying waste water. It is directed particularly to such systems of the electrolytic type.
One method of purifying waste water is to introduce very small bubbles ("microbubbles") into it. The microbubbles adhere to particulates and other impurities in the waste water and lift them to the surface. The water can thereby be purified by skimming a layer of froth from the water surface. There are many varieties of flotation systems, but most fall into one of two categories: the pressurized-air type and the electrolytic type.
In the pressurized-air type, air may be introduced into the waste water under pressure, causing it to dissolve in the waste water. The pressure is then relieved, and the air comes out of solution in the form of microbubbles. In other versions of the pressurized-air system, the air is introduced into waste water at atmospheric pressure by means of a device that ensures that the bubbles formed in the waste water are small. The small bubble size is important because small bubbles have more of a tendency to adhere to impurities. They are also more efficient, tending to float a greater mass of waste for a given mass of air.
The other type of flotation system, the electrolytic system, is considerably simpler in construction. It consists simply of electrodes disposed in a tank through which the waste water flows. A potential difference is imposed between the electrodes, and the resultant current through the waste water causes electrolysis of the water to generate hydrogen and oxygen bubbles. These bubbles then perform the flotation in a manner similar to that in which bubbles in pressurized-air systems do.
Clearly, the electrolytic system is considerably simpler in design and thus requires less of an initial investment. The electrolytic system does not require the compressors, high-pressure pumps, and pressure-monitoring devices that pressurized-air systems do. Nonetheless, the pressurized-air systems have been considerably more popular. The reason for this is that electrolytic systems use a high amount of energy per unit mass of solids removed.
It is accordingly an object of the present invention to reduce the power requirements of electrolytic flotation systems so as to enable users to take advantage of their low capital requirements.